1. Field of the Invention
The invention relates to controllable vibration dampers for motor vehicles, The damper includes a cylinder which contains a damping medium and an axially movable piston rod sealed and submerged in the medium A damping piston is attached to the piston rod and subdivides the cylinder into a two work chambers. The damping piston has passages which are controlled by valve discs. The valve discs have their outer diameter of one face resting on a leading edge of and on their opposite face side their inner circumference is supported with a second leading edge.
2. Background Information
Hydraulic vibration dampers are already known. For example U.S. Pat. No. 3,312,312 shows a damping piston design in which valve discs having their outer dimensions resting on an outer edge or ledge in the piston on the opposite face or side of the discs the inner circumferences are supported by a second ledge or edge. Passages in the damping piston are controlled by the valve discs, and provide tension and pressure modes of operation of the damping process. Control for a change of the dampening force at the valve discs is not provided in this vibration damper.
Beyond this, controllable vibration dampers are known, for example German Patent No. 37 19 113, which corresponds to U.S. Pat. No. 4,880,086, entitled "Adjustable Vibration Damper", where an infinitely variable damping valve is contemplated. Since such a damping valve can only be subject to flow from one side, the utilization of this damping valve is primarily limited to a bypass system in a two-tube type of vibration damper. The application of this damping valve in a gas pressure damper or in a spring cylinder does not require a reworking of the vibration damper itself whereby corresponding check valves must permit the one-sided flow into the damping valve.